Factors affecting the dissolution rate of novolac resins II: developer composition effects

Resist function depends upon photoinduced changes in the dissolution rate of phenolic polymer films in aqueous base. The events that occur as the molecules in these films move from the glassy state into solution are not well understood. This paper presents an extensive study of the influence of developer composition and concentration on the dissolution rate of novolac films in aqueous base. The dissolution rate is shown to be a function of both the cation and anion composition and concentration in the developer at a constant pH. When salts are added to the base, the rate first increases, reaches a maximum, and then decreases with increasing salt concentration. In the concentration regime below the maximum, the rate increases linearly with cation concentration and is independent of anion composition. The dissolution of novolac is dependent on cation concentration and not ionic strength in this regime. In the concentration regime above the maximum, the composition of the anion has a marked influence on the rate.